The objective of this research project will be to further study the interaction between glucocorticoids and somatomedin, specifically as related to GAGS biosynthesis and glucocorticoid receptors in cartilage cells. Both of the hormones are essential for optimal growth, yet, in large doses, glucocorticoids inhibit growth and somatomedin stimulates growth, especially in cartilage. The interaction of these two hormones on specific steps in GAGS biosynthesis, and, in addition, the effects of somatomedin on the binding of glucocorticoids to sterospecific cartilage glucocorticoid receptors. Demonstration of a reciprocal action of these two hormones may greatly aid in our understanding of the mechanism of glucocorticoid induced growth retardation, as well as our understanding of the effects of somatomedin stimulation on long bone growth. A further objective of this research will be to further study the effects of glucocorticoids on embryonic cardiac tissue. We observed that embryonic chick hearts are greatly enlarged after glucocorticoid administration, while in the same embryo, cartilage growth and GAGS biosynthesis was markedly inhibited. We proposed to study the effect of glucocorticoid on cartilage and cardiac tissue as to content, histology, GAGS biosynthesis, development of sterospecific glucocorticoid receptors and induction of specific enzyme systems. These studies may greatly aid our understanding of the mechanism of glucocorticoid induced growth retardation as well as provide further insight as to the interaction of somatomedin with other hormones which facilitate or inhibit cartilage growth. BIBLIOGRAPHIC REFERENCES: Reeves, R.D., Dickinson, L., Lee J., Kilgore, B., Branham, B., Elders, M.J.: Effects of Dietary Composition on Somatomedin Activity in Growing Rats. Clin. Res. Vol 25, No. 1, p 68A, Jan 1977. (abstract) Kilgore, B., Lee, J.A., Hughes, E.R., Elders, M.J.: Stimulation of Xylose Incorporation into an Acceptor Protein by a Partially Purified Serum Factor. Clin. Res. Vol 25, No. 1, p 68A, Jan. 1977 (abstract).